Field of the Invention
The present invention relates to a heat exchanger to be used as a constitutional element of a water heater.
Description of the Related Art
One embodiment of a heat exchanger is disclosed in Patent Literature 1.
The disclosed heat exchanger has a pair of header portions for water inflow and water outflow on a side plate member of a case housing a plurality of heat transfer tubes. Each header portion is constituted in such a manner that a bulging portion bulging out of the case is formed on the side plate member of the case and that a wall portion for header constituted with an auxiliary member is fitted onto and welded to the bulging portion. End portions of the heat transfer tubes are welded to a tip end wall portion of the bulging portion. Thus, a chamber communicating with the heat transfer tubes is formed by the side plate member of the case and the wall portion for header of the auxiliary member.
In such a configuration, water is able to appropriately flow into or from the heat transfer tubes using the pair of header portions. The header portions are formed utilizing the side plate member of the case, thereby reducing the number of members and the size of installation, and in addition, reducing the production cost.
However, the above conventional art has the following disadvantages.
The pair of header portions provided for the side plate member of the case are constituted in such a manner that two wall portions for headers which are separately formed using the auxiliary members are welded to the side plate member of the case. Therefore, for producing the header portions, two wall portions for headers are respectively manufactured in advance and are positioned relative to the side plate member of the case, and welding is respectively executed. Such a production procedure of the header portions is rather complicated.
On the other hand, as to a heat exchanger other than the above, Patent Literature 2 discloses another heat exchanger. In Patent Literature 2, the heat exchanger uses a helical heat transfer tube as a plurality of heat transfer tubes. Some heat transfer tubes are not helical tubes, and have smaller entire length and smaller flow path resistance than the helical heat transfer tube. Such a configuration reduces the pressure loss generated at the time of flowing water into the heat transfer tubes. When the non-helical heat transfer tube is provided in addition to the helical heat transfer tube in order to reduce the pressure loss, the configuration of the heat exchanger is complicated.